This is what the graph looks like
if the sequence goes on without any changes
it will be d+8a
You have a 300 feet side length square and you need to calculate the length of the diagonal. When you split the square along one diagonal you get triangles, so you can apply Pythagoras' Theorem, with the hypotenuse as the needed diagonal.
a²+b²=c²
300²+300²=c²
2*300²=c²
√(2*300²)=c
√(2) * √(300²)=c
√(2) * 300=c
c~424.26 ft which is the solution/option c
C is the least that is beause it is .015 which is smaller than 0.15